Porous copper body, porous copper composite part, method for manufacturing porous copper body, and method for manufacturing porous copper composite part

ABSTRACT

A porous copper body including a skeleton having a three-dimensional network structure is provided. An oxidation-reduction layer formed by an oxidation-reduction treatment is provided on a surface of the skeleton, and the oxygen concentration of the entirety of the skeleton is set to be 0.025 mass % or less.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending application: “POROUS COPPERBODY, POROUS COPPER COMPOSITE PART, METHOD FOR MANUFACTURING POROUSCOPPER BODY, AND METHOD FOR MANUFACTURING POROUS COPPER COMPOSITE PART”filed even date herewith in the names of Koichi KITA; Jun KATO andToshihiko SAIWAI as a national phase entry of PCT/JP2016/065122, whichapplication is assigned to the assignee of the present application andis incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a porous copper body made of copper ora copper alloy, a porous copper composite part in which the porouscopper body is bonded to a main body of the composite part, a method formanufacturing the porous copper body, and a method for manufacturing theporous copper composite part.

Priority is claimed on Japanese Patent Application No. 2015-119523,filed on Jun. 12, 2015, the content of which is incorporated herein byreference.

BACKGROUND ART

The above-mentioned porous copper body and the porous copper compositepart are used, for example, as electrodes and current collectors invarious batteries, heat exchanger components, silencing components,filters, impact-absorbing components, and the like.

For example, PTL 1 discloses a heat transfer member having athree-dimensional network structure which is obtained by sintering apowder made of copper or a copper alloy as a raw material in a reductionatmosphere.

PTL 2 discloses a heat exchange member in which a porous copper layer isformed on a surface of a copper tube by sintering a copper powder.

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application, First Publication No.H08-145592

PTL 2: Japanese Unexamined Patent Application, First Publication No.H11-217680

SUMMARY OF INVENTION Technical Problem

In PTL 1, sintering is performed in an inert gas atmosphere or areduction atmosphere. In PTL 2, a powder made of copper or a copperalloy is used as a raw material, and the raw material powder istemporarily bonded to a surface of a copper tube using a binder,followed by an oxidation treatment and a reduction treatment to sinterthe copper raw material and form a porous copper layer. As described inPTL 1 and PTL 2, when performing only sintering in an inert gasatmosphere or a reduction atmosphere, a metal bond of copper isinsufficient, and there is a concern that thermal conductivity orelectrical conductivity may be insufficient.

The present invention has been made in consideration of theabove-described circumstances, and an objective thereof is to provide aporous copper body in which copper raw materials are sufficiently bondedto each other and which is particularly excellent in thermalconductivity and electrical conductivity, a porous copper composite partin which the porous copper body is bonded to a main body of thecomposite part, a method for manufacturing the porous copper body, andmethod for manufacturing the porous copper composite part.

Solution to Problem

To solve the above-described problem and to accomplish theabove-described objective, a porous copper body according to an aspectof the present invention (hereinafter, referred to as “porous copperbody of the present invention”) includes a skeleton having athree-dimensional network structure, in which an oxidation-reductionlayer formed by an oxidation-reduction treatment is provided on asurface of the skeleton, and an oxygen concentration of an entirety ofthe skeleton is set to be 0.025 mass % or less.

According to the porous copper body having such configuration, since theporous copper body includes the oxidation-reduction layer formed by theoxidation-reduction treatment on the surface of the skeleton, a specificsurface area increases. Therefore, for example, it is possible togreatly improve heat exchange efficiency and the like.

Since the oxygen concentration of the entirety of the skeleton is set tobe 0.025 mass % or less, copper raw materials are sufficientlymetal-bonded through the oxidation-reduction treatment, and thus thermalconductivity and electrical conductivity are particularly excellent.

In the porous copper body of the present invention, it is preferablethat a specific surface area of an entirety of the porous copper body beset to be 0.01 m²/g or greater, and a porosity of the entirety of theporous copper body be set to be in a range of 50% to 90%.

In this case, the specific surface area is set to be great, and theporosity is set to be high. Therefore, for example, it is possible tosurely improve heat exchange efficiency and the like.

In the porous copper body of the present invention, it is preferablethat the skeleton be constituted by a sintered body made of a pluralityof copper fibers, and in each of the copper fibers, a diameter R be setto be in a range of 0.02 mm to 1.0 mm, and a ratio L/R of a length L tothe diameter R be set to be in a range of 4 to 2500.

In this case, the copper fibers in which the diameter R is set to be ina range of 0.02 mm to 1.0 mm, and the ratio L/R of the length L to thediameter R is set to be in a range of 4 to 2500, are sintered.Therefore, voids are sufficiently retained between the copper fibers,and a shrinkage ratio in the sintering can be limited. Accordingly, itis possible to raise the porosity, and the dimensional accuracy isexcellent.

A porous copper composite part according to another aspect of thepresent invention (hereinafter, referred to as “porous copper compositepart of the present invention”) includes: a main body of the compositepart; and the above-described porous copper body bonded to the main bodyof the composite part.

According to the porous copper composite part having such configuration,the porous copper body having excellent stability of surface propertiesis strongly bonded to the main body of the composite part. Therefore, asthe porous copper composite part, excellent thermal conductivity andexcellent electrical conductivity can be exhibited.

In the porous copper composite part of the present invention, it ispreferable that a bonding surface of the main body of the compositepart, to which the porous copper body is bonded, be made of copper or acopper alloy, and the porous copper body and the main body of thecomposite part be bonded to each other through sintering.

In this case, the porous copper body and the main body of the compositepart are integrally bonded to each other through the sintering, and thusthe porous copper body and the main body of the composite part arestrongly bonded to each other. Therefore, as the porous copper compositepart, excellent thermal conductivity and excellent electricalconductivity are exhibited.

A method for manufacturing a porous copper body according to stillanother aspect of the present invention (hereinafter, referred to as“method for manufacturing a porous copper body of the presentinvention”) is a method for manufacturing the above-described porouscopper body which includes: a skeleton forming step of forming theskeleton having the oxygen concentration of 0.025 mass % or less; and anoxidation-reduction step of forming the oxidation-reduction layer on thesurface of the skeleton.

According to the method for manufacturing the porous copper body havingsuch configuration, the method includes: the skeleton forming step offorming the skeleton having an oxygen concentration of 0.025 mass % orless; and the oxidation-reduction step of forming theoxidation-reduction layer on the surface of the skeleton. Therefore, itis possible to obtain a porous copper body in which a specific surfacearea increases, copper raw materials are sufficiently metal-bondedthrough the oxidation-reduction treatment, and thermal conductivity andelectrical conductivity are particularly excellent.

The method for manufacturing the porous copper body of the presentinvention may further include: a copper raw material lamination step oflaminating a copper raw material having an oxygen concentration of 0.03mass % or less; and a sintering step of sintering a plurality of thecopper raw materials which are laminated. In the sintering step, thecopper fibers may be oxidized and then the oxidized copper fibers may bereduced, thereby bonding the copper fibers to each other so as to formthe skeleton and forming the oxidation-reduction layer on the surface ofthe skeleton. That is, in the method for manufacturing the porous copperbody, the above-described skeleton forming step and theoxidation-reduction step are performed in the copper raw materiallamination step and the sintering step.

In this case, the copper raw materials having an oxygen concentration of0.03 mass % or less are used, and thus it is possible to set an oxygenconcentration in the porous copper body after sintering to be 0.025 mass% or less. In the sintering step, the copper fibers are oxidized, andthen the oxidized copper fibers are reduced and are bonded to eachother, and thus it is possible to form the oxidation-reduction layer onthe surface of the skeleton.

The method for manufacturing the porous copper body of the presentinvention may further include a preliminary reduction treatment ofdecreasing the oxygen concentration of the copper raw materials.

In this case, since the method includes the preliminary reductiontreatment of decreasing the oxygen concentration of the copper rawmaterials, it is possible to limit the oxygen concentration of thecopper raw materials to 0.03 mass % or less, and it is possible to setthe oxygen concentration in the porous copper body after sintering to be0.025 mass % or less.

A method for manufacturing a porous copper composite part according tostill another aspect of the present invention (hereinafter, referred toas “method for manufacturing a porous copper composite part of thepresent invention”) is a method for manufacturing a porous coppercomposite part in which includes: a main body of the composite part; anda porous copper body bonded to the main body of the composite part. Themethod includes a bonding step of bonding the porous copper bodymanufactured by the above-described method for manufacturing the porouscopper body, and the main body of the composite part to each other.

According to the method for manufacturing a porous copper composite parthaving such configuration, the porous copper body manufactured by theabove-described method for manufacturing the porous copper body isprovided, and thus it is possible to manufacture a porous coppercomposite part having excellent thermal conductivity and electricalconductivity.

In the method for manufacturing a porous copper composite part of thepresent invention, it is preferable that, a bonding surface of the mainbody of the composite part, to which the porous copper body is bonded,be made of copper or a copper alloy, and the porous copper body and themain body of the composite part be bonded to each other throughsintering.

In this case, the main body of the composite part and the porous copperbody can be integrated with each other through the sintering, and thusit is possible to manufacture a porous copper composite part havingexcellent thermal conductivity and electrical conductivity.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a porouscopper body in which copper raw materials are sufficiently bonded toeach other and which is particularly excellent in thermal conductivityand electrical conductivity, a porous copper composite part in which theporous copper body is bonded to a main body of the composite part, amethod for manufacturing the porous copper body, and method formanufacturing the porous copper composite part.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an enlarged schematic view of a porous copper body accordingto a first embodiment of the present invention.

FIG. 2 is a flowchart showing an example of a method for manufacturingthe porous copper body shown in FIG. 1.

FIG. 3 is a view showing a manufacturing process of manufacturing theporous copper body shown in FIG. 1.

FIG. 4 is a view showing an external appearance of a porous coppercomposite part according to a second embodiment of the presentinvention.

FIG. 5 is a flowchart showing an example of a method for manufacturingthe porous copper composite part shown in FIG. 4.

FIG. 6 is an external view of a porous copper composite part accordingto another embodiment of the present invention.

FIG. 7 is an external view of a porous copper composite part accordingto still another embodiment of the present invention.

FIG. 8 is an external view of a porous copper composite part accordingto still another embodiment of the present invention.

FIG. 9 is an external view of a porous copper composite part accordingto still another embodiment of the present invention.

FIG. 10 is an external view of a porous copper composite part accordingto still another embodiment of the present invention.

FIG. 11 is an external view of a porous copper composite part accordingto still another embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a porous copper body, a porous copper composite part, amethod for manufacturing the porous copper body, and a method formanufacturing the porous copper composite part according to embodimentsof the present invention will be described with reference to theaccompanying drawings.

First Embodiment

First, a porous copper body 10 according to a first embodiment of thepresent invention will be described with reference to FIG. 1 to FIG. 3.

As shown in FIG. 1, the porous copper body 10 according to thisembodiment includes a skeleton 12 formed by sintering a plurality ofcopper fibers 11.

Each of the copper fibers 11 is made of copper or a copper alloy. Inthis embodiment, for example, each of the copper fibers 11 is made ofC1100 (tough pitch copper). In the copper fiber 11, a diameter R is setto be in a range of 0.02 mm to 1.0 mm, and a ratio L/R of a length L tothe diameter R is set to be in a range of 4 to 2500.

In this embodiment, the copper fibers 11 are subjected to shapeimparting such as twisting and bending.

In the porous copper body 10 according to this embodiment, an apparentdensity D_(A) is set to be 51% or less of a true density D_(T) of thecopper fibers 11. The shape of each copper fiber 11 is an arbitraryshape, such as a linear shape and a curved shape, as long as theapparent density D_(A) is 51% or less of the true density D_(T) of thecopper fibers 11. However, when using the copper fibers 11 in which atleast a part thereof is subjected to a processing for imparting apredetermined shape such as twisting and bending, it is possible to formvoids between fibers in a three-dimensional and isotropic shape. As aresult, it is possible to improve the isotropy of various propertiessuch as the heat transfer properties and the electrical conductivity ofthe porous copper body 10.

The copper fibers 11 are manufactured through adjustment into apredetermined equivalent circle diameter by a drawing method, a coilcutting method, a wire cutting method, a melt-spinning method and thelike, length adjustment for satisfying predetermined L/R, and cutting.

The equivalent circle diameter R is a value calculated on the basis of across-sectional area A of each fiber, and is defined by the followingexpression on the assumption of a true circle regardless of across-sectional shape.R=(A/π)^(1/2)×2

In the porous copper body 10 according to this embodiment, anoxidation-reduction layer is formed on a surface of the skeleton 12(copper fibers 11). In bonding portions between the copper fibers 11,oxidation-reduction layers formed on surfaces of the copper fibers 11are integrally bonded to each other.

Each of the oxidation-reduction layers has a porous structure, andcauses minute unevenness on the surface of skeleton 12 (copper fibers11). According to this, a specific surface area of the entirety of theporous copper body 10 is set to be 0.01 m²/g or greater, and a porositythereof is set to be in a range of 50% to 90%.

Although not particularly limited, the upper limit of the specificsurface area of the entirety of the porous copper body 10 is 0.50 m²/g.

Although not particularly limited, a range of the specific surface areaof the entirety of the porous copper body 10 is preferably 0.03 m²/g to0.40 m²/g, and more preferably 0.05 m²/g to 0.30 m²/g. Similarly,although not particularly limited, a range of the porosity is 60% to90%, and more preferably 70% to 90%.

In the porous copper body 10 according to this embodiment, an oxygenconcentration of the entirety of the skeleton 12 is set to be 0.025 mass% or less.

The lower limit of the oxygen concentration of the entirety of theskeleton 12 is a value depending on a grade of copper used, and is notparticularly limited. The lower limit of the oxygen concentration in acase of using oxygen-free copper is approximately 0.00001 mass %.

Next, a method for manufacturing the porous copper body 10 according tothis embodiment will be described with reference to a flowchart in FIG.2, a process diagram of FIG. 3, and the like.

First, copper fibers 11 having the oxygen concentration of 0.03 mass %or less are prepared. In this embodiment, for example, a preliminaryreduction treatment step S00 is performed on copper fibers 11 having anoxygen concentration of approximately 0.05 mass %, and thereby theoxygen concentration of the copper fibers 11 is decreased to 0.03 mass %or less. By this preliminary reduction treatment step S00, an oxygenamount, particularly, on the surfaces of the copper fibers 11, isdecreased. Even in a case where the oxygen concentration of the copperfibers 11 is 0.03 mass % or less before performing the preliminaryreduction treatment step S00, by performing the preliminary reductiontreatment step S00, it is possible to increase the cleanness of thesurfaces of the copper fibers 11.

In this embodiment, conditions of the preliminary reduction treatmentstep S00 are set such that the atmosphere is a mixed gas atmosphere ofargon and hydrogen, the holding temperature is in a range of 350° C. to850° C., and the holding time is in a range of 5 minutes to 120 minutes.

In a case where the holding temperature in the preliminary reductiontreatment step S00 is lower than 350° C., there is a concern that thecopper fibers 11 cannot be sufficiently reduced and thus the oxygenconcentration of the copper fibers 11 cannot be decreased. On the otherhand, in a case where the holding temperature in the preliminaryreduction treatment step S00 is higher than 850° C., there is a concernthat the copper fibers 11 may be sintered with each other in thepreliminary reduction treatment step S00.

From the above, in this embodiment, the holding temperature in thepreliminary reduction treatment step S00 is set to be 350° C. to 850° C.It is preferable to set the lower limit of the holding temperature inthe preliminary reduction treatment step S00 to be 400° C. in order tosufficiently decrease the oxygen concentration of the copper fibers 11.It is preferable that the upper limit of the holding temperature be 800°C. in order to surely suppress sintering of the copper fibers 11 in thepreliminary reduction treatment step S00.

In a case where the holding time in the preliminary reduction treatmentstep S00 is shorter than 5 minutes, there is a concern that the copperfibers 11 cannot be sufficiently reduced and thus the oxygenconcentration cannot be decreased. On the other hand, in a case wherethe holding time in the preliminary reduction treatment step S00 islonger than 120 minutes, there is a concern that the copper fibers 11may be sintered with each other in the preliminary reduction treatmentstep S00.

From the above, in this embodiment, the holding time in the preliminaryreduction treatment step S00 is set to be in a range of 5 minutes to 120minutes. It is preferable that the lower limit of the holding time inthe preliminary reduction treatment step S00 be set to be 10 minutes inorder to sufficiently decrease the oxygen concentration of the copperfiber 11. It is preferable that the upper limit of the holding time beset to be 100 minutes in order to surely suppress sintering of thecopper fibers 11 in the preliminary reduction treatment step S00.

Next, as shown in FIG. 3, the copper fibers 11 after the preliminaryreduction treatment step S00 are distributed from a distributor 31toward the inside of a stainless-steel container 32 to bulk-fill thestainless-steel container 32. Thereby, the copper fibers 11 arelaminated (copper fibers lamination step S01).

In the copper fibers lamination step S01, a plurality of the copperfibers 11 are laminated so that a bulk density D_(P) after the fillingbecomes 50% or less of the true density D_(T) of the copper fibers 11.In this embodiment, the copper fibers 11 are subjected to a processingfor imparting a shape such as twisting and bending, and thus it ispossible to retain three-dimensional and isotropic voids between thecopper fibers 11 during lamination.

Next, the copper fibers 11 bulk-filling the stainless-steel container 32are subjected to an oxidation-reduction treatment (oxidation-reductiontreatment step S02).

As shown in FIG. 2 and FIG. 3, the oxidation-reduction treatment stepS02 includes: an oxidation treatment step S21 of performing an oxidationtreatment on the copper fibers 11, and a reduction treatment step S22 ofreducing and sintering the copper fibers 11 subjected to the oxidationtreatment.

In this embodiment, as shown in FIG. 3, the stainless-steel container 32filled with the copper fibers 11 is put in a heating furnace 33 andheated in an air atmosphere to perform an oxidation treatment on thecopper fibers 11 (oxidation treatment step S21). Through the oxidationtreatment step S21, an oxide layer, for example, with a thickness of 1μm to 100 μm is formed on a surface of each of the copper fibers 11.

Conditions of the oxidation treatment step S21 in this embodiment areset such that the holding temperature is in a range of 520° C. to 1050°C. and the holding time is in a range of 5 minutes to 300 minutes.

In a case where the holding temperature in the oxidation treatment stepS21 is lower than 520° C., there is a concern that the oxide layers arenot sufficiently formed on the surfaces of the copper fibers 11. On theother hand, in a case where the holding temperature in the oxidationtreatment step S21 is higher than 1050° C., there is a concern thatoxidation may progress to the inside of the copper fibers 11.

From the above, in this embodiment, the holding temperature in theoxidation treatment step S21 is set to be 520° C. to 1050° C. In theoxidation treatment step S21, it is preferable that the lower limit ofthe holding temperature be set to be 600° C., and the upper limit of theholding temperature be set to be 1000° C. in order to surely form theoxide layers on the surfaces of the copper fibers 11.

In a case where the holding time in the oxidation treatment step S21 isshorter than 5 minutes, there is a concern that the oxide layers may notbe sufficiently formed on the surfaces of the copper fibers 11. On theother hand, in a case where the holding time in the oxidation treatmentstep S21 is longer than 300 minutes, there is a concern that oxidationmay progress to the inside of the copper fibers 11.

From the above, in this embodiment, the holding time in the oxidationtreatment step S21 is set to be in a range of 5 minutes to 300 minutes.It is preferable that the lower limit of the holding time in theoxidation treatment step S21 be set to be 10 minutes in order to surelyform the oxide layers on the surfaces of the copper fibers 11. It ispreferable that the upper limit of the holding time in the oxidationtreatment step S21 be set to be 100 minutes in order to surely suppressoxidation on the inside of the copper fibers 11.

In this embodiment, as shown in FIG. 3, after performing the oxidationtreatment step S21, the stainless steel container 32 filled with thecopper fibers 11 is put in the heating furnace 34 and is heated in areduction atmosphere. According to this, the oxidized copper fibers 11are subjected to a reduction treatment to form an oxidation-reductionlayer, and the copper fibers 11 are bonded to each other to form theskeleton 12 (reduction treatment step S22).

Conditions of the reduction treatment step S22 in this embodiment areset such that the atmosphere is a mixed gas atmosphere of argon andhydrogen, the holding temperature is in a range of 600° C. to 1080° C.,and the holding time is in a range of 5 minutes to 300 minutes.

In a case where the holding temperature in the reduction treatment stepS22 is lower than 600° C., there is a concern that the oxide layersformed on the surfaces of the copper fibers 11 may not be sufficientlyreduced. On the other hand, in a case where the holding temperature inthe reduction treatment step S22 is higher than 1080° C., the copperfibers are heated to near the melting point of copper, and thus there isa concern that strength and porosity may decrease.

From the above, in this embodiment, the holding temperature in thereduction treatment step S22 is set to be 600° C. to 1080° C. It ispreferable that the lower limit of the holding temperature in thereduction treatment step S22 be set to be 650° C. in order to surelyreduce the oxide layers formed on the surfaces of the copper fibers 11.It is preferable that the upper limit of the holding temperature in thereduction treatment step S22 be set to be 1050° C. in order to surelylimit a decrease in strength and the porosity.

In a case where the holding time in the reduction treatment step S22 isshorter than 5 minutes, there is a concern that the oxide layers formedon the surfaces of the copper fibers 11 may not be sufficiently reducedand sintering may become insufficient. On the other hand, in a casewhere the holding time in the reduction treatment step S22 is longerthan 300 minutes, there is a concern that thermal shrinkage due to thesintering may increase and strength may decrease.

From the above, in this embodiment, the holding time in the reductiontreatment step S22 is set to be in a range of 5 minutes to 300 minutes.It is preferable that the lower limit of the holding time in thereduction treatment step S22 be set to be 10 minutes in order to surelyreduce the oxide layers formed on the surfaces of the copper fibers 11and to allow sintering to sufficiently progress. It is preferable thatthe upper limit of the holding time in the reduction treatment step S22be set to be 100 minutes in order to surely limit thermal shrinkage dueto the sintering or a decrease in strength.

An oxidation-reduction layer is formed on the surface of the copperfibers 11 (skeleton 12) by the oxidation treatment step S21 and thereduction treatment step S22 and thus minute unevenness is formed.

The oxide layers are formed on the surfaces of the copper fibers 11 bythe oxidation treatment step S21, and a plurality of the copper fibers11 are cross-linked through the oxide layers. Then, by performing thereduction treatment step S22, the oxide layers formed on the surfaces ofthe copper fibers 11 are reduced so as to form the above-describedoxidation-reduction layers. In addition, the oxidation-reduction layersare bonded to each other and thereby the copper fibers 11 are sinteredso as to form the skeleton 12.

According to the manufacturing method as described above, the copperfibers 11 are sintered so as to form the skeleton 12, and theoxidation-reduction layer is formed on the surface of the skeleton 12(copper fibers 11). The oxygen concentration of the entirety of theskeleton 12 is set to be 0.025 mass % or less, and thus the porouscopper body 10 according to this embodiment is manufactured.

According to the porous copper body 10 of this embodiment describedabove, since the oxygen concentration of the entirety of the skeleton 12is set to be 0.025 mass % or less, the copper fibers 11 are surelymetal-bonded by the oxidation treatment step S21 and the reductiontreatment step S22, and thus the thermal conductivity and the electricalconductivity are particularly excellent.

In a case where the oxygen concentration of the entirety of the skeleton12 is greater than 0.025 mass %, there is a concern that the metalbonding of the copper fibers 11 may become insufficient and thus thethermal conductivity and the electrical conductivity may deteriorate.

From the above, in this embodiment, the oxygen concentration of theentirety of the skeleton 12 is set to be 0.25 mass % or less. It ispreferable that the oxygen concentration of the entirety of the skeleton12 be set to be 0.02 mass % or less in order to further improve thethermal conductivity and electrical conductivity.

In the porous copper body 10 according to this embodiment, the skeleton12 is formed by sintering the copper fibers 11 in which the diameter Ris set to be in a range of 0.02 mm to 1.0 mm, and the ratio L/R of thelength L to the diameter R is set to be in a range of 4 to 2500.Therefore, voids are sufficiently retained between the copper fibers 11,and it is possible to limit the shrinkage ratio in the sintering. As aresult, the porosity is high and the dimensional accuracy is excellent.

This embodiment includes the copper fibers lamination step S01 in whichthe copper fibers 11 having the diameter R in a range of 0.02 mm to 1.0mm and the ratio L/R of the length L to the diameter R in a range of 4to 2500 are laminated so that the bulk density D_(P) is 50% or less ofthe true density D_(T) of the copper fibers 11. Therefore, it ispossible to retain voids between the copper fibers 11 and limitshrinkage. According to this, it is possible to manufacture the porouscopper body 10 having high porosity and excellent dimensional accuracy.

Specifically, the apparent density D_(A) of the porous copper body 10which is manufactured by sintering the copper fibers 11 laminated sothat the bulk density D_(P) is 50% or less of the true density D_(T) ofthe copper fibers 11, is set to be 51% or less of the true density D_(T)of the copper fibers 11. Therefore, shrinkage during the sintering islimited, and thus a high porosity can be retained.

In a case where the diameter R of the copper fibers 11 is less than 0.02mm, there is a concern that a bonding area between the copper fibers 11may be small and thus sintering strength may be deficient. On the otherhand, in a case where the diameter R of the copper fibers 11 is greaterthan 1.0 mm, there is a concern that the number of contact points atwhich the copper fibers 11 come into contact with each other may bedeficient and thus the sintering strength may be deficient.

From the above, in this embodiment, the diameter R of the copper fibers11 is set to be in a range of 0.02 mm to 1.0 mm. It is preferable thatthe lower limit of the diameter R of the copper fibers 11 be set to be0.05 mm, and the upper limit of the diameter R of the copper fibers 11be set to be 0.5 mm in order to further improve strength.

In a case where the ratio L/R of the length L to the diameter R of thecopper fibers 11 is less than 4, it is difficult for the bulk densityD_(P) to be 50% or less of the true density D_(T) of the copper fibers11 when laminating the copper fibers 11, and thus there is a concernthat it is difficult to obtain the porous copper body 10 with a highporosity. On the other hand, in a case where the ratio L/R of the lengthL to the diameter R of the copper fibers 11 is greater than 2500, thereis a concern that the copper fibers 11 cannot be uniformly dispersed andthus it is difficult to obtain the porous copper body 10 with a uniformporosity.

From the above, in this embodiment, the ratio L/R of the length L to thediameter R of the copper fibers 11 is set to be in a range of 4 to 2500.It is preferable that the lower limit of the ratio L/R of the length Lto the diameter R of the copper fibers 11 be set to be 10 in order tofurther improve porosity. It is preferable that the upper limit of theratio L/R of the length L to the diameter R of the copper fibers 11 beset to be 500 in order to surely obtain the porous copper body 10 with auniform porosity.

The method for manufacturing the porous copper body according to thisembodiment includes: the oxidation treatment step S21 of oxidizing thecopper fibers 11; and the reduction treatment step S22 of reducing theoxidized copper fibers 11. Therefore, it is possible to form theoxidation-reduction layer on the surface of the copper fibers 11(skeleton 12).

In the method for manufacturing the porous copper body according to thisembodiment, the copper fibers 11 of which the oxygen concentration isset to be 0.03 mass % or less by the preliminary reduction treatmentstep S00, are used. Thus, it is possible to set the oxygen concentrationof the entirety of the skeleton 12 to be 0.025 mass % or less.

Second Embodiment

A porous copper composite part 100 according to a second embodiment ofthe present invention will be described with reference to theaccompanying drawings.

FIG. 4 shows the porous copper composite part 100 according to thisembodiment. The porous copper composite part 100 includes: a copperplate 120 (main body of the composite part) made of copper or a copperalloy; and a porous copper body 110 bonded to the surface of the copperplate 120.

In the porous copper body 110 according to this embodiment, a pluralityof copper fibers are sintered to form a skeleton in the same manner asin the first embodiment. The copper fibers are made of copper or acopper alloy, and have a diameter R set to be in a range of 0.02 mm to1.0 mm, and a ratio L/R of a length L to the diameter R set to be in arange of 4 to 2500. In this embodiment, the copper fibers are made of,for example, oxygen-free copper.

In this embodiment, the copper fibers are subjected to shape impartingsuch as twisting and bending. In the porous copper body 110 according tothis embodiment, an apparent density D_(A) thereof is set to be 51% orless of a true density D_(T) of the copper fibers.

In this embodiment, by performing an oxidation-reduction treatment (anoxidation treatment and a reduction treatment) as described later, anoxidation-reduction layers are formed on the surfaces of the copperfibers (skeleton) constituting the porous copper body 110 and the copperplate 120. Thereby, minute unevenness is formed on the surfaces ofcopper fibers (skeleton) and the copper plate 120. In this embodiment, aspecific surface area of the entirety of the porous copper body 110 isset to be 0.01 m²/g or greater, and the porosity thereof is set to be ina range of 50% to 90%.

An oxidation-reduction layer formed on the surface of the copper fibersand an oxidation-reduction layer formed on the surface of the copperplate 120 are integrally bonded to each other at bonding portionsbetween the surfaces of the copper fibers constituting the porous copperbody 110 and the copper plate 120.

In this embodiment, the oxygen concentration of the entirety of theskeleton of the porous copper body 110 is set to be 0.025 mass % orless.

The lower limit of the oxygen concentration of the entirety of theskeleton 12 is a value depending on a grade of copper used, and is notparticularly limited. In a case where the oxygen-free copper is used,the lower limit of the oxygen concentration is approximately 0.00001mass %.

Next, a method for manufacturing the porous copper composite part 100according to this embodiment will be described with reference to aflowchart in FIG. 5.

First, the copper plate 120 as a main body of the composite part isprepared (copper plate-disposing step S100). Copper fibers with anoxygen concentration of 0.03 mass % or less are dispersed and laminatedon the surface of the copper plate 120 (copper fibers lamination stepS101). In the copper fibers lamination step S101, a copper fiber with anoxygen concentration of 0.03 mass % or less is used, and a plurality ofthe copper fibers are laminated so that a bulk density D_(P) is 50% orless of a true density D_(T) of the copper fibers.

Next, the copper fibers laminated on the surface of the copper plate 120are sintered to shape the porous copper body 110 and to bond the porouscopper body 110 and the copper plate 120 to each other (a sintering stepS102 and a bonding step S103). As shown in FIG. 5, the sintering stepS102 and the bonding step S103 include: an oxidation treatment step S121of performing an oxidation treatment of the copper fibers and the copperplate 120; and a reduction treatment step S122 of reducing and sinteringthe copper fibers and the copper plate 120 having subjected to theoxidization treatment.

In this embodiment, the copper plate 120 on which the copper fibers arelaminated is put in a heating furnace, and is heated in an airatmosphere to perform an oxidization treatment on the copper fibers(oxidation treatment step S121). According to the oxidation treatmentstep S121, for example, oxide layers with a thickness of 1 μm to 100 μmare formed on the surfaces of the copper fibers and the copper plate120.

Conditions of the oxidation treatment step S121 in this embodiment areset such that the holding temperature is in a range of 520° C. to 1050°C. and preferably 600° C. to 1000° C., and the holding time is in arange of 5 minutes to 300 minutes and preferably 10 minutes to 100minutes.

In this embodiment, after performing the oxidation treatment step S121,the copper plate 120 on which the copper fibers are laminated is put ina sintering furnace, and is heated in a reduction atmosphere to performa reduction treatment on the oxidized copper fibers and the oxidizedcopper plate 120. Thereby, the copper fibers are bonded to each otherand the copper fibers and the copper plate 120 are bonded to each other(reduction treatment step S122).

Conditions of the reduction treatment step S122 in this embodiment areset such that the atmosphere is a mixed gas atmosphere of nitrogen andhydrogen, the holding temperature is in a range of 600° C. to 1080° C.and preferably 650° C. to 1050° C., and the holding time is in a rangeof 5 minutes to 300 minutes and preferably 10 minutes to 100 minutes.

By the oxidation treatment step S121 and the reduction treatment stepS122, an oxidation-reduction layer is formed on the surfaces of thecopper fibers (skeleton) and the copper plate 120 and minute unevennessis formed.

Oxide layers are formed on the surfaces of the copper fibers (skeleton)and the copper plate 120 by the oxidation treatment step S121. Throughthe oxide layers, a plurality of the copper fibers are cross-linked toeach other and to the copper plate 120. Then, by performing thereduction treatment S122, the oxide layers formed on the surfaces of thecopper fibers (skeleton) and the copper plate 120 are reduced. Thereby,the copper fibers are sintered through the oxidation-reduction layer toform the skeleton and the porous copper body 110 and the copper plate120 are bonded to each other.

According to the manufacturing method as described above, the porouscopper composite part 100 according to this embodiment is manufactured.

According to the porous copper composite part 100 of this embodimentdescribed above, since the oxygen concentration of the entirety of theskeleton of the porous copper body 110 is set to be 0.025 mass % orless, the copper fibers 11 are surely metal-bonded to each other by theoxidation treatment step S121 and the reduction treatment step S122, andthe thermal conductivity and the electrical conductivity areparticularly excellent.

In the porous copper composite part 100 according to this embodiment,the porous copper body 110 is obtained through sintering of the copperfibers having the diameter R set to be in a range of 0.02 mm to 1.0 mmand the ratio L/R of the length L to the diameter R set to be in a rangeof 4 to 2500, and thus has a high porosity and excellent strength anddimensional accuracy. This porous copper body 110 is bonded to thesurface of the copper plate 120. Therefore, various properties thereof,such as the heat transfer properties and the electrical conductivity,are excellent.

In this embodiment, the oxidation-reduction layer is formed on thesurfaces of the copper fibers constituting the porous copper body 110and the copper plate 120, the specific surface area of the entirety ofthe porous copper body 110 is set to be 0.01 m²/g or greater, and theporosity thereof is set to be in a range of 50% to 90%. Therefore, it ispossible to greatly improve heat exchange efficiency and the like.

Although not particularly limited, the upper limit of the specificsurface area of the entirety of the porous copper body 110 is 0.50 m²/g.

Although not particularly limited, the specific surface area of theentirety of the porous copper body 110 is preferably 0.03 m²/g to 0.40m²/g and more preferably 0.05 m²/g to 0.30 m²/g. Similarly, although notparticularly limited, the porosity is preferably 60% to 90%, and morepreferably 70% to 90%.

In this embodiment, an oxidation-reduction layer formed on the surfaceof the copper fibers and an oxidation-reduction layer formed on thesurface of the copper plate 120 are integrally bonded to each other atbonding portions between the surfaces of the copper fibers constitutingthe porous copper body 110 and the copper plate 120. Therefore, theporous copper body 110 and the copper plate 120 are strongly bonded toeach other, and thus various properties thereof, such as the strength ofa bonding interface, the heat transfer properties, and the electricalconductivity are excellent.

According to the method for manufacturing the porous copper compositepart 100 of this embodiment, the oxygen-free copper with an oxygenconcentration of 0.03 mass % or less is used as the copper fibers, andthus the oxygen concentration of the entirety of the skeleton of theporous copper body 110 can be set to be 0.025 mass % or less.

In the method for manufacturing the porous copper composite part 100according to this embodiment, the copper fibers are laminated on thesurface of the copper plate 120 made of copper or a copper alloy, andthe sintering step S102 and the bonding step S103 are simultaneouslyperformed. Therefore, it is possible to simplify the manufacturingprocess.

Hereinbefore, the embodiments of the present invention were described.However, the present invention is not limited thereto and can beappropriately modified in a range not departing from the technical ideaof the invention.

For example, although the embodiments are described such that the porouscopper body is manufactured using a manufacturing facility shown in FIG.3, there is no limitation thereto and the porous copper body can bemanufactured using another manufacturing facility.

The atmosphere of the oxidation treatment steps S21 and S121 has only tobe an oxidation atmosphere in which copper or a copper alloy is oxidizedat a predetermined temperature. Specifically, the atmosphere is notlimited to the air atmosphere, and has only to be an atmosphere in which10 vol % or greater of oxygen is contained in an inert gas (for example,nitrogen). The atmosphere of the reduction treatment steps S22 and S122has only to be a reduction atmosphere in which a copper oxide is reducedinto metal copper or the copper oxide is decomposed at a predeterminedtemperature. Specifically, it is possible to suitably use anitrogen-hydrogen mixed gas or an argon-hydrogen mixed gas whichcontains several vol % or greater of hydrogen, a pure hydrogen gas, oran ammonia decomposed gas or a propane decomposed gas which isindustrially used in many cases, and the like.

In addition, although the embodiments are described such that copperfibers made of tough pitch copper (JIS C1100) or oxygen-free copper (JISC1020) are used, there is no limitation thereto and as a material of thecopper fibers 11, it is possible to suitably use phosphorus deoxidizedcopper (JIS C1201, C1220), silver-containing copper (for example,Cu-0.02 to 0.5 mass % of Ag), chromium copper (for example, Cu-0.02 to1.0 mass % of Cr), zirconium copper (for example, Cu-0.02 to 1.0 mass %of Zr), tin-containing copper (for example, Cu-0.1 to 1.0 mass % of Sn),and the like. Particularly, in a case of being used in ahigh-temperature environment of 200° C. or higher, it is preferable touse the silver-containing copper, the chromium copper, thetin-containing copper, the zirconium-containing copper and the like,which are excellent in high-temperature strength.

Although the embodiments are described such that the skeleton of theporous copper body is formed by sintering the copper fibers, there is nolimitation thereto and it is possible to set the oxygen concentration ofthe entirety of the skeleton to be 0.025 mass % or less by using aporous copper body such as fiber non-woven fabric and a metal filterhaving the oxygen concentration of 0.03 mass % or less, or by using aporous copper body as a raw material such as fiber non-woven fabric anda metal filter in which the oxygen concentration is decreased to 0.03mass % or less by performing the preliminary reduction treatment S00,and the same effect is expected.

In the second embodiment, although the porous copper composite parthaving a structure shown in FIG. 4 is described as an example, there isno limitation thereto and a porous copper composite part having astructure as shown in FIG. 6 to FIG. 11 may be employed.

For example, as shown in FIG. 6, a porous copper composite part 200 inwhich a plurality of copper tubes 220 as a main body of the compositepart are inserted into a porous copper body 210, may be employed.

Alternatively, as shown in FIG. 7, a porous copper composite part 300 inwhich a copper tube 320 as a main body of the composite part curved in aU-shape is inserted into a porous copper body 310, may be employed.

As shown in FIG. 8, a porous copper composite part 400 in which a porouscopper body 410 is bonded to an inner peripheral surface of a coppertube 420 as a main body of the composite part, may be employed.

As shown in FIG. 9, a porous copper composite part 500 in which a porouscopper body 510 is bonded to an outer peripheral surface of a coppertube 520 as a main body of the composite part, may be employed.

As shown in FIG. 10, a porous copper composite part 600 in which porouscopper bodies 610 are bonded to an inner peripheral surface and an outerperipheral surface of a copper tube 620 as a main body of the compositepart, may be employed.

As shown in FIG. 11, a porous copper composite part 700 in which porouscopper bodies 710 are bonded to both surfaces of a copper plate 720 as amain body of the composite part, may be employed.

EXAMPLES

Hereinafter, results of a confirmation experiment carried out to confirmthe effect of the present invention will be described.

Porous copper bodies including a skeleton with a three-dimensionalnetwork structure was manufactured using raw materials shown in Table 1.

An oxidation-reduction treatment was performed under conditions shown inTable 2 so as to manufacture porous copper bodies having 30 mm ofwidth×200 mm of length×5 mm of thickness. In Inventive Examples 3 to 7,9, and 10, a preliminary reduction treatment step was performed underconditions shown in Table 2.

Regarding each of the obtained porous copper bodies, oxygenconcentration, porosity, and relative electrical conductivity thereofwere evaluated. Evaluation results are shown in Table 3. An evaluationmethod will be described below.

(Fiber Diameter R)

As the fiber diameter R, an average value of an equivalent circlediameter (Heywood diameter) R=(A/π)^(1/2)×2, which was calculatedthrough image analysis on the basis of JIS Z 8827-1 using a particleanalyzer “Morphologi G3” manufactured by Malvern Instruments Ltd., wasused.

(Fiber Length L)

As the fiber length L of the copper fibers, a simple average value,which was calculated through image analysis using the particle analyzer“Morphologi G3” manufactured by Malvern Instruments Ltd., was used.

(Oxygen Concentration of Fiber)

Approximately 1 g of copper fiber was put into a gas analyzer (modelnumber: TCEN-600) manufactured by LECO CORPORATION, and an oxygenconcentration (mass %) in the copper fiber was measured by an inert gasfusion method where a helium gas was used as a carrier gas.

(Oxygen Concentration C_(O) of Porous Copper Body)

Approximately 1 g of a sample was cut out from the obtained porouscopper body and was put into the gas analyzer (model number: TCEN-600)manufactured by LECO CORPORATION, and then the oxygen concentrationC_(O) (mass %) was measured by the inert gas fusion method where ahelium gas was used as a carrier gas.

(Apparent Density Ratio D_(A)/D_(T), and Porosity P)

A mass M (g) and a volume V (cm³) of the obtained porous copper body,and a true density D_(T) (g/cm³) of the copper fibers constituting theporous copper body were measured, and the apparent density RatioD_(A)/D_(T), and the porosity P (%) were calculated using the followingexpressions. The true density D_(T) was measured by an under-watermethod using a precision balance.D _(A) /D _(T) =M/(V×D _(T))P=(1−(M/(V×D _(T))))×100

(Relative Electrical Conductivity C_(R)) A sample having 10 mm ofwidth×500 mm of length×5 mm of thickness was cut out from the obtainedporous copper body, and electrical conductivity C₁ (S/m) was measured bya four terminal method on the basis of JIS C2525. The relativeelectrical conductivity C_(R) (%) was obtained based on electricalconductivity C₂ (S/m) of a bulk material which constitutes the porouscopper body and is made of copper or a copper alloy, and the apparentdensity ratio D_(A)/D_(T) of the porous copper body using the followingexpression.C _(R)(%)=C ₁/(C ₂×(D _(A) /D _(T)))×100

TABLE 1 Copper fiber Oxygen Fiber diameter R concentration Material (mm)L/R (mass %) Inventive 1 C1020 0.10 50 0.002 Examples 2 C1020 0.05 2500.002 3 C1020 0.10 150 0.002 4 C1020 0.10 25 0.002 5 C1100 0.02 500 0.046 C1100 0.10 60 0.04 7 C1100 0.80 15 0.04 8 C1220 0.20 35 0.01 9 C12200.20 120 0.01 10 C1441 0.08 50 0.01 Comparative 1 C1020 0.10 80 0.002Examples 2 C1020 0.10 80 0.002

TABLE 2 Manufacturing process Preliminary reduction treatment stepOxidation treatment step Reduction treatment step Temperature TimeTemperature Time Temperature Time Atmosphere (° C.) (min) Atmosphere (°C.) (min) Atmosphere (° C.) (min) Inventive 1 — — — Air 750 150 N₂—3% H₂750 90 Examples 2 — — — Air 700 60 N₂—3% H₂ 700 60 3 N₂—3% H₂ 500 90 Air820 30 N₂—3% H₂ 950 90 4 Ar—10% H₂ 850 5 Air 620 60 N₂—3% H₂ 620 270 5N₂—3% H₂ 650 100 Air 570 240 N₂—3% H₂ 900 90 6 N₂—3% H₂ 750 10 Air 63060 N₂—3% H₂ 800 90 7 100% H₂ 400 120 Air 850 10 N₂—3% H₂ 1080 10 8 — — —Air 780 30 Ar—10% H₂ 1000 180 9 Ar—10% H₂ 800 60 Air 800 60 Ar—10% H₂900 90 10 N₂—3% H₂ 750 100 Air 680 90 Ar—10% H₂ 950 60 Comparative 1 — —— — — — N₂—3% H₂ 800 30 Examples 2 — — — Air 950 60 — — —

TABLE 3 Porous copper body Oxygen Relative electrical concentrationPorosity conductivity (mass %) (%) (%) Inventive 1 0.002 71 30.3Examples 2 0.002 82 26.4 3 0.002 64 45.2 4 0.002 87 36.7 5 0.012 78 22.56 0.022 73 17.4 7 0.015 53 19.9 8 0.007 65 28.4 9 0.008 70 24.5 10 0.00574 21.8 Comparative 1 0.002 67 8.6 Examples 2 0.060 68 3.5

In Comparative Example 2 in which the oxygen concentration of theentirety of the porous copper body was greater than 0.025 mass %, therelative electrical conductivity was less than 10%.

In contrast, in Inventive Examples 1 to 10 in which the oxygenconcentration of the entirety of the porous copper body was set to be0.025 mass % or less, the relative electrical conductivity wassufficiently high.

As described above, it was confirmed that it is possible to provide aporous copper body excellent in thermal conductivity and electricalconductivity according to the Inventive Examples.

INDUSTRIAL APPLICABILITY

It is possible to provide a porous copper body with particularlyexcellent thermal conductivity and electrical conductivity, a porouscopper composite part in which the porous copper body is bonded to amain body of the composite part, a method for manufacturing the porouscopper body, and method for manufacturing the porous copper compositepart. For example, the present invention is applicable to electrodes andcurrent collectors in various batteries, heat exchanger components,silencing members, filters, impact-absorbing members, and the like.

REFERENCE SIGNS LIST

-   -   10, 110 Porous copper body    -   11 Copper fiber    -   12 Skeleton    -   100 Porous copper composite part    -   120 Copper plate (Main body of the composite part)

The invention claimed is:
 1. A porous copper body, comprising: askeleton having a three-dimensional network structure, wherein anoxidation-reduction layer formed by an oxidation-reduction treatment isprovided on a surface of the skeleton, an oxygen concentration of anentirety of the skeleton is set to be 0.025 mass % or less, and arelative electrical conductivity is in a range of 17.4% to 45.2%.
 2. Theporous copper body according to claim 1, wherein a specific surface areaof an entirety of the porous copper body is set to be 0.01 m²/g orgreater, and a porosity of the entirety of the porous copper body is setto be in a range of 50% to 90%.
 3. The porous copper body according toclaim 1, wherein the skeleton is constituted by a sintered body made ofa plurality of copper fibers, and in each of the copper fibers, adiameter R is set to be in a range of 0.02 mm to 1.0 mm, and a ratio L/Rof a length L to the diameter R is set to be in a range of 4 to
 2500. 4.A porous copper composite part, comprising: a main body of the compositepart; and the porous copper body according to claim 1 bonded to the mainbody of the composite part.
 5. The porous copper composite partaccording to claim 4, wherein a bonding surface of the main body of thecomposite part, to which the porous copper body is bonded, is made ofcopper or a copper alloy, and the porous copper body and the main bodyof the composite part are bonded to each other through sintering.
 6. Theporous copper body according to claim 2, wherein the skeleton isconstituted by a sintered body made of a plurality of copper fibers, andin each of the copper fibers, a diameter R is set to be in a range of0.02 mm to 1.0 mm, and a ratio L/R of a length L to the diameter R isset to be in a range of 4 to
 2500. 7. A porous copper composite part,comprising: a main body of the composite part; and the porous copperbody according to claim 2 bonded to the main body of the composite part.8. A porous copper composite part, comprising: a main body of thecomposite part; and the porous copper body according to claim 3 bondedto the main body of the composite part.
 9. The porous copper bodyaccording to claim 3, wherein the ratio L/R is in a range of 4 to 50.